In recent years, a small-sized portable device has become widespread globally, and at the same time, along with significant development of a high-speed information transmission network, demand for a small-sized large capacity non-volatile memory is increasing rapidly. Especially, a NAND type flash memory, and a small-sized HDD (hard disk drive) have experienced rapid evolution of recording density, and have developed a large market.
Under these circumstances, some concepts for new memory have been proposed to exceed the current limit of recording density significantly. For example, PRAM (phase change memory) uses a material capable of having two states of an amorphous state (OFF) and a crystalline state (ON) as a recording material, adopts an operational process in which data is recorded by associating these two states with binary data “0” and “1
For writing/erasing, an amorphous state is formed by applying high power pulses to the recording material and a crystalline state is formed by applying low power pulses to the recording material, for example.
Reading is performed by passing, through the recording material, a read current that is small enough not to cause the writing/erasing, and thereby measuring the electric resistance of the recording material. The resistance value of the recording material in an amorphous state is greater than the resistance value of the recording material in a crystalline state, and their ratio is, for example, approximately 103.
In these storage devices, an electrode layer (barrier layer) is provided in some cases in order to establish electrical connection to a recording layer, or to prevent diffusion of an element between the recording layer and interconnection or rectifying element. In this case, the electrode layer is usually provided at both ends of the recording layer in the direction of applied electric field. For example, the electrode layers are provided between the recording layer and the interconnection, and between the recording layer and the rectifying element, respectively. As a material of the electrode layers, for example, metal nitride is used, and these electrode layers are composed of the same material in general (for example, refer to JP-A 2007-287761 (Kokai)).